The invention relates to a system for measuring the movement between a nuclear reactor core support barrel and adjacent reactor structure such as the reactor vessel surrounding the barrel.
Nuclear reactor vessel walls are, typically, annular vertically oriented metallic structures having an inner annular core support barrel supported from an integral flange thereof at the top of the reactor vessel wall in closely spaced relation to the annular inside surface of the vessel. A plurality of core stabilizer lugs or reactor vessel snubber lugs, or both, are located at spaced positions around and within the annular space between the reactor vessel and the core barrel to insure that an adequate annular space is maintained.
It is desirable and important to maintain a gap between the annular core barrel on one side and the opposing structure, be it a reactor wall, mating snubber structure, lug or thermal shield guide pin, on the other side of the annular space. Accordingly, there is a need to provide a means and method of measuring the clearance between the core barrel and the reactor vessel structure or other reactor internal structure. For example, measurements between a reactor vessel wall lug and the core barrel wall within the vessel at a plurality of peripheral points would be useful.
Schemes utilizing conventional ultrasonics and electrical contacts have been proposed for this purpose. However, it is known that gas turbine engine fuel control systems utilize yet a third principal to be investigated. The instant invention utilizes that third principal, namely, two orifices in series in which the downstream orifice's effective area is variable.